Five essentials for choosing the right energy system for battery test applications
Disruptive Change: From Combustion Engines to E-Motors Julia Wolf (M.A.) Heinzinger Electronic The major trend of electromobility is currently the biggest driver in the automotive industry. It is presenting OEMs and suppliers with tremendous challenges and permanently changing the rules of play in the automotive sector. Suddenly, the combustion engine is no longer the most important core area of expertise, but instead it is energy stores, power electronics, e-motors or even entire e-axles that are in demand. The winners and losers of this boom of tomorrow are being decided in the development departments of today. The industry is working on new solutions to make our mobility eco-friendly and economical with resources. High costs, short ranges and long charging times have in the past been reasons why car buyers preferred combustion engines over electromobility. So car manufacturers, suppliers and service providers are working flat-out to move electromobility forward. The e-motor, and especially the battery, form the focus of attention, since they determine the range and driving behavior. Development of voltages and power for electromobility With the progress of electromobility, the demands for test equipment are changing. 48 Volt are already standard, voltages among 1,000 and higher gain further recognition. Previously we talked about power in the area of a few kilowatts, now more than 100 kW is necessary – in some instances there is the necessity of megawatts. Conventional power supplies quickly reach their limits, in regard to connect power parallel to meet the required currents at all. The keyword for this solution is “flexible output”. According to the most recent status, this is the opportunity to build your system flexible and to expand it at a later time – cost-conscious with long-term security of investment. But voltages and current on their own do not compose a battery tester or simulator. A number of further attributes should be considered when searching for the best fitting test system for your application: Security of investment through enhancement options Flexibility for different applications through the combination of any different output channels Realistic behaviour with high dynamic by compensation of current steps or changes Safety for test object, power supply and user Sustainability for a reliable system If these criteria were taken into account, companies are on the safe side when choosing the components for their test benches. Security of investment through enhancement options The already described changes in the demands of voltages and power in the automotive sector are showing, how important it is to build the system future-oriented, well prepared for future requirements. The option to upgrade your existing system at a future time with additional output channels or the possibility to connect them, should be offered. The option to connect or cascading further channels do not only offer flexibility (see on next point) but also security of the investment in the long-term. But of prime importance for every test house should be the ability to use the same hardware for battery tests and for battery simulation, simply by switching the software. Flexibility for different applications through the combination of any different output channels Point one and two are closely linked together: For the validation of prototypes, preliminary series and constantly changing products or subsystems, a high level of flexibility is essential. High quality technics and modern test bench concepts, which enable practical and realistic test with highest accuracy, are the crucial components. The possibility to use the several outputs as single or as multi-channel-system with serial or parallel connection, allows the option to build various current/voltage ranges and offers the best application security, especially for future requirements. The knowledge, that you are able to select, whether a system should rather deliver high current or high voltage up to 1200V, gives a feeling of satisfaction. A very essential point concerning the paralleling of output channels needs to be addressed carefully. It is essential, that a real Master-/Slave operation of the power supply itself is implemented. If the paralleling of different channels or even power units is attempted by an overall automation system, the desired high dynamic behavior may be significantly influenced. The reason being that nonspecific systems are not able to guarantee the necessary precise harmonization of current or power sharing. If you pay attention to these options while choosing your power supply, you will get a system, which is able to meet different demands – whether it is for validation, quality control or end-of-Line testing. Realistic behaviour with high dynamic by compensation of current steps or changes It is here that the wheat is separated from the chaff of the manufacturers of battery tester and battery simulators. To test a battery to the limit of its capacity, it is important, that the system is working precise enough, to adjust current rapidly. Minimum and maximum setting values have to be configurable for the application of battery tests. To get valid and reproducible data during battery simulation, the rule is, that decreasing the voltage in small amounts, will result in more realistic simulation of the behavior of the battery. Minimal voltage-overshoots are also a sign for a high level of control of the system and an important aspect in regard to the security of the connected test object, because in the worst case a big voltage-overshoot could destroy it. Safety for test object, power supply and user Avoiding of uncontrolled charging and discharging currents To make sure, that a battery is evaluated correctly and the state of charge of the connected memory will not be changed, e.g. the “currentless connection” of batteries is an important parameter. This approach is protecting the battery from damages, because it secures that both sides of the protection have the same voltage potential. When a battery is connected to the DC controller, any uncontrolled charging or discharging currents from the battery must therefore be avoided. The battery voltage should be measured via a sensing input at the consumer before the battery is connected. Based on this measurement, the internal control circuit (which is equipped with a decoupling capacitor)
